BACKGROUND/AIMS: This study compared the efficacy and safety of combined peginterferon alfa (PEG-IFN) and ribavirin with that of combined interferon alpha (IFN-alpha) and ribavirin, according to the treatment duration in Korean patients with chronic hepatitis C. METHODS: Medical records of 86 patients treated with PEG-IFN and ribavirin (mean age, 50.7 years; males/females, 57/29; genotypes 1/2, 59/27) and 134 patients treated with IFN-alpha and ribavirin (mean age, 50.9 years; males/females 74/60; genotypes 1/2, 79/55) were reviewed. Ribavirin was administered at doses of 600-1,200 mg and 600-800 mg in patients with genotypes 1 and 2, respectively. RESULTS: Sustained virological responses (SVRs) were evident in 68.4% and 41.7% of genotype 1 patients treated for 48 weeks in the PEG-IFN and IFN-alpha groups, respectively (P=0.021), and in 94.1% and 64.9% of genotype 2 patients treated for 24 weeks (P=0.026). Some genotype 1 patients treated for 24 weeks in the PEG-IFN group, who all exhibited negative HCV PCR results at week 12, showed an SVR of 87.5% (7/8). CONCLUSIONS: The rate of SVRs in Korean patients with chronic hepatitis C was higher for combined PEG-IFN and ribavirin than for combined IFN-alpha and ribavirin. Further study is needed to clarify the outcome of short-term therapy in patients with a rapid or early virological response.